This invention relates to a fuel regulation apparatus for an engine for a model for regulating supply of fuel according to rotational frequency which is mounted to the engine for the model which pressurizes the fuel by varying air pressure generated in a crankcase when driving.
A carburetor has been conventionally used in a two-stroke cycle or four-stroke cycle glow engine as a means for regulating quantity of fuel supplied to a combustion chamber of the engine.
The present applicant has proposed an engine for a model equipped with a fuel injection apparatus instead of the carburettor. In this engine, air pressure generated in a crankcase is introduced into a combustion tank through a check valve and stored in the tank and fuel is pressurized to 20-100kPa.
The pressure generated in the crankcase of the engine varies depending on rotational frequency, that is to say, it is high at the time of high speed rotation, and it is low at the time of low speed rotation. Therefore, the fuel tank is constructed so that the maximum pressure can be stored therein. It is, however, difficult in practice to maintain stably a constant pressure, for example, at 30-40 kPa.
Therefore, a regulator has been conventionally used in order to control constantly the pressure of fuel supplied from the fuel tank to feed to a fuel injection apparatus. The regulator is an apparatus for passing only the fuel having a certain given pressure.
In a conventional engine of a model which pressurizes the fuel by air pressure in a crankcase and injects the fuel by a fuel injection apparatus, it is premised that the pressure of the fuel is constant, and the supply of the fuel is controlled by injection time. That is to say, when the rotational frequency is low, the injection time is shortened to decrease the quantity of the fuel, and when the rotational frequency is high, the injection time is lengthened to increase the quantity of the fuel.
At the time of low speed, however, the pressure of the fuel rises since the quantity of the fuel used is small, and the fuel becomes dense. And, since the quantity of the fuel used per unit time is large at the time of high speed, the supply of the fuel is not sufficient, and the fuel becomes thin. Therefore, in the conventional engine for a model, the rotation of the engine is unstable and it is possible in some instances that overheat takes place at the time of high speed and engine stop takes place at the time of low speed.